Sen. Dennis Stowell, R-Parowan, told the Legislature's Revenue and Taxation Interim Committee on Wednesday that he plans to run a bill in 2008 that would change the way county assessors arrive at a property's market value, which is currently based on sales data of comparable properties.

Stowell's legislation would base calculations on a five-year rolling average of property values, which would flatten out any potential spikes in value.

A sharp increase in values for a single year would only cause a slight increase in the five-year average, said Utah County Assessor Kris Poulson.

But because the Utah Constitution states that properties are assessed in proportion to their fair market value, Stowell's legislation, if passed, would require a change in that wording.

Two-thirds of legislators in the state's House of Representatives and Senate would have to approve the amendment and then submit it to a vote of Utah residents. "I believe people are so upset over fluctuating vales, we could pass a constitutional amendment," Stowell said.